1. Field of the Invention
The present invention relates to a semiconductor memory. In particular, the present invention relates to a nonvolatile memory having a plurality of memory cells that can be written once (also referred to as a nonvolatile semiconductor memory).
2. Description of the Related Art
As a semiconductor memory, there are a DRAM (Dynamic Random Access Memory), a SRAM (Static Random Access Memory), a flash memory, an EEPROM (Electrically Erasable Programmable Read Only Memory), and the like. As these memories have large capacities, there is high probability that a defective bit exists even in an advanced manufacturing process. As for a conventional large capacity memory, a redundant circuit is provided and a defective bit is modified after manufacturing a chip; therefore, a yield may be improved and the cost may be reduced. Specifically, a memory is inspected before the shipment. When there is a defective bit, such setting that an fuse within a redundant circuit is disconnected is configured for a memory having the defective bit, and the memory is shipped after restoring the defective bit (for example, see Reference 1: Keeth Baker, “DRAM: Circuit Design A TUTORIAL”, IEEE PRESS, 2001, P. 108-109).